Insights into the Genetic Profile of Two Siblings Affected by Unverricht-Lundborg Disease Using Patient-Derived hiPSCs

Abstract

Unverricht-Lundborg disease (ULD), also known as progressive myoclonic epilepsy 1 (EPM1), is a rare autosomal recessive neurodegenerative disorder characterized by a complex symptomatology that includes action- and stimulus-sensitive myoclonus and tonic-clonic seizures. The main cause of the onset and development of ULD is a repeat expansion of a dodecamer sequence localized in the promoter region of the gene encoding cystatin B (CSTB), an inhibitor of lysosomal proteases. Although this is the predominant mutation found in most patients, the physio-pathological mechanisms underlying the disease complexity remain largely unknown. In this work, we used patient-specific iPSCs and their neuronal derivatives to gain insight into the molecular and genetic machinery responsible for the disease in two Italian siblings affected by different phenotypes of ULD. Specifically, fragment length analysis on amplified CSTB promoters found homozygous status for dodecamer expansion in both patients and showed that the number of dodecamer repeats is the same in both. Furthermore, the luciferase reporter assay showed that the CSTB promoter activity was similarly reduced in both lines compared to the control. This information allowed us to draw important conclusions: (1) the phenotypic differences of the patients do not seem to be strictly dependent on the genetic mutation around the CSTB gene, and (2) that some other molecular mechanisms, not yet clearly identified, might be taken into account. In line with the inhibitory role of cystatin B on cathepsins, molecular investigations performed on iPSCs-derived neurons showed an increased expression of lysosomal cathepsins (B, D, and L) and a reduced expression of CSTB protein. Intriguingly, the increase in cathepsin expression does not appear to be correlated with the residual amount of CSTB, suggesting that other mechanisms, in addition to the regulation of cathepsins, could be involved in the pathological complexity of the disease.

Unraveling the impact of ZZZ3 on the mTOR/ribosome pathway in human embryonic stem cells homeostasis

“…Human pluripotent stem cells (PSCs), comprising ESCs and induced PSCs, possess the unique capability to self-renew and differentiate into any of the three germ layers ( Evans and Kaufman, 1981 ; Parrotta et al., 2019a ; Thomson et al., 1998 ). These features make them valuable for diverse biomedical applications including enhancing our understanding of early human development ( Zhu and Huangfu, 2013 ), disease modeling ( Lucchino et al., 2022 ; Orban et al., 2015 ; Scalise et al., 2022 ), drug discovery ( Chen et al., 2018 ), regenerative medicine ( Parrotta et al., 2019b ), and personalized medicine ( Shi et al., 2017 ). To harness their potential, understanding the molecular mechanisms governing pluripotency is crucial.…”

ZZZ3 protects human embryonic stem cells from nucleolar stress by boosting mTOR/ribosome pathway

“…Pluripotent stem cells (PSCs), including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have the unique capability to self-renew while remaining competent to differentiate into any of the three germ layers (1,2,40). These features make human pluripotent stem cells extremely attractive for various biomedical applications including the understanding of early human developmental processes (41), disease modeling (42)(43)(44), drug discovery (45), regenerative medicine (46), and personalized medicine (47). For these applications to serve for basic and translational research, a thorough and comprehensive understanding of the molecular mechanisms controlling pluripotency is required.…”

Mosaic midbrain organoids: a new tool to study Progressive Supranuclear Palsy and advancing clinical neurology research

“…The copyright holder for this preprint (which this version posted June 3, 2024. ; https://doi.org/10.1101/2024.06.03.597136 doi: bioRxiv preprint induced pluripotent stem cell (iPSC) technology has revolutionized our capacity to recapitulate inaccessible cell types, offering valuable insights into the mechanisms of various diseases, especially neurological disorders [16][17][18] . iPS-derived cerebral organoids have emerged as a powerful tool able to recapitulate architectural and functional features of the human brain, offering a robust in vitro model for studying neurological disorders 19,20 also at early stages of the disease.…”